A circular pool with a sand-beach entrance and shower-massaging fountain. Private cabanas, cocktail service, and couple-sized wading pools fit for canoodling. There are even blackjack tables -- with bikini-clad dealers, no less -- a few steps from the water’s edge. And there’s not a water slide or a roller coaster in sight.

Now, that’s what I call a waterpark.

Actually, it’s called The Backyard, and it’s located at the Red Rock Casino, Resort and Spa, which opened on the outskirts of Las Vegas last spring. Built to chill -- not to thrill -- the three-acre oasis is an idyllic spot to say goodbye to summer and ease into autumn.

Summer, after all, is the season for theme parks, camping trips, and other family-focused vacations. And while I like traveling with the kids as much as the next guy, sometimes I can’t wait for the bell to ring on the first day of school. Come fall, I’m ready to go somewhere that doesn’t involve robotic presidents, spinning tea cups, or photo ops with some guy in a Goofy suit.

Like Las Vegas, where cool style and cooler temperatures come together to create the perfect autumn getaway for grown-ups. From sleek spas and swanky nightspots to hotel rooms that are downright racy, here’s a look at some of the newest indulgences in Sin City:

Red Rock Casino, Resort and Spa (www.redrocklasvegas.com/): Located in Summerlin, 10 miles west of downtown, this resort stands in stark contrast to the themed behemoths on The Strip. You won’t find a faux Eiffel Tower or updated Doge’s Palace, but rather a sleek, luxe look that mimics the desert-oasis resorts of the ‘50s and ‘60s. Think Rat Pack meets the St. Regis with the best amenities $1 billion can buy.

Slideshow: Vegas then and now
Opened in May 2006, the resort features 414 guestrooms and suites, nine restaurants, and five bars. Step into the casino, spa, or Cherry nightclub -- run by über-impresario Rande Gerber -- and you can enjoy the sinfully indulgent activity of your choice. A second tower with expanded spa facilities and another 436 rooms is expected to open in early 2007.

In the meantime, The Backyard pool area is the place to be. Settle into a lounge chair, soak up some sun and a signature drink, and you, too, may find yourself saying a toast to the start of the school year.

Palms Casino Resort (www.palms.com/): If Red Rock strives for understated elegance, the Palms Casino Resort, just west of The Strip, is a glittering citadel of sexy sizzle. Ever since MTV’s The Real World was filmed here in 2002, the resort has been Vegas’ crib of choice for rock stars, Hollywood hunks, and the celebutante set.

This spring, the resort unveiled its latest offering -- a new tower with a selection of Fantasy Suites that might make the hooked-up hotties on TRW blush. Ranging from 1,500 to 4,200 square feet, each one is a uniquely themed playpen for guests who like to live large.

Take the Erotic Suite, for example, which features a rotating bed, mirrored ceiling, and leather-and-metal decor that suggests the Marquis de Sade. Or how about the Crib Suite, which boasts a DJ booth and hydraulic bed that would make Snoop Dogg swoon? Both come with Show Showers, glass-walled enclosures with special lighting and their very own dancer poles. Maybe it’s just me, but I’m not sure getting clean is the goal.

With teams using more than 100 unique apparatuses to launch globular projectiles a half-mile or more, the 27th annual World Championship Punkin Chunkin event is our pick as November’s Weird Festival of the Month.

There are also more PG-rated rooms -- try the Hardwood Suite, complete with its half basketball court, or the bowling-alley-equipped King Pin Suite -- but there’s no denying the Fantasy Tower’s adult orientation. With the first new Playboy Club in 25 years expected to open atop the tower the first week in October, this is obviously not Stratosphere or Circus Circus.

Caesars Palace (www.harrahs.com/): Let’s face it, all that dancing, drinking, and late-night desiring can be exhausting. At Caesars, the solution is simple -- a spa treatment at Qua, the resort’s newest shrine to self-indulgence, which is scheduled to open in October.

Part Roman bathhouse, part New Age retreat, Qua was designed as a 50,000-square-foot pamper palace with three pools, 51 treatment rooms, and an extensive menu of exotic services. There are Roman baths for “social spa-ing,” couple’s studios for more private procedures, and even an Arctic Ice Room, where guests can use ice chips to exfoliate, invigorate, and generally cool down should any treatment get too hot.

Qua’s most exotic offering, however, will probably be the Crystal Room, where guests can have tiny Swarovski crystals adhered to their bodies in any number of customized designs. Billed as “the ultimate accessory,” they promise to add even more sparkle to whatever excitement the evening holds in store. Just make sure you take them off before you get home -- it might be tough explaining them to the kids.

The grand tradition of the gap year: that glorious time between school and work when young people take an extended break to see the world, explore their options and, perhaps, get a better sense of how they want to live the rest of their lives. These days, more people facing middle age are wondering why young people should have all the fun.